Paper number 524

INFLUENCE OF MATRIX CRACKS AND SWELLING ON MOISTURE ABSORPTION IN CROSS-PLY GFRP LAMINATES.

Jan-Erik Lundgren and Peter Gudmundson

Department of Solid Mechanics, Royal Institute of Technology
SE-100 44 Stockholm, Sweden

Summary

Moisture uptake in cross-ply glass fibre/epoxy laminates containing matrix cracks in transverse plies are investigated. Experimental results are compared to both finite element calculations and an approximative analytic model. The experimental results show that crack closure may occur early in the absorption process. This is confirmed by finite element calculations which indicate that even small amounts of absorbed moisture (average moisture concentration < 10 % of saturation level) may result in crack closure. As a result of crack closure, surrounding moisture environment penetration through the crack channels is pre-vented. The experimentally observed small differences in moisture uptake between cracke and uncracked laminates thus support the crack closure hypothesis. Direct microscopic obser-vations of crack closure versus time furthermore confirm the mechanism. A previously devel-oped analytic model has been extended to include the case of crack closure effects. The model compare favourable with the experimental observation.

Keywords

moisture absorption, matrix cracks, experiment, finite element calculation, analytical model.